Impression cylinder

ABSTRACT

A printing cylinder for particularly flexo-printing machines and indirect photogravure printing machines, in which either end of the sleeve is provided with an adjusting mechanism which is in engagement with the shaft. The sleeve is mounted with such clearance on the shaft that during rotation, the shaft cannot come into contact with the internal surface of the sleeve. Preferably each adjusting mechanism consists of three adjusting screws. Preferably the sleeve consists of an inner tubular cylinder of steel or aluminium and an outer tubular cylinder of foamed polyurethane. The printing cylinder produces a sharp imprint of high quality at high peripheral speeds, e.g., 200 meters/minute of the printing cylinder.

United States Patent 1 Christoffersen 1 51 Jan. 7,1975

[ IMPRESSION CYLINDER 21 Appl. No.: 338,556

[301' Foreign Application Priority Data Mar. 6, 1972 Denmark 1029/72 [52] U.S. Cl. 29/132, 29/110 [51] Int. Cl B21b 31/08 [58] Field of Search 29/130, 132, 110

{56] References Cited UNITED STATES PATENTS 1,687,498' 10/1928 Jaek 29/130 X 2,005,885 6/1935 Brindley 29/130 X 2,312,762 3/1943 Fauffman 29/130 X 3,475,803 11/1969 Hill 29/132 3,613,316 10/1971 Eten 29/130 X 3,693,544 9/1972 Trzyna 29/132 X 3,757,398 9/1973 Urban 29/132 X FOREIGN PATENTS OR APPLICATIONS Primary Examiner Alfred R. Guest Attorney, Agent, or FirmBucknam and Archer 57 ABSTRACT A printing cylinder for particularly flexo-printing machines and indirect photogravure printing machines, in which either end of the sleeve is provided with an adjusting mechanism which is in engagement with the shaft. The sleeve is mounted with such clearance on the shaft that during rotation, the shaft cannot come into contact with the internal surface of the sleeve. Preferably each adjusting mechanism consists of three adjusting screws. Preferably the sleeve consists of an inner tubular cylinder of steel or aluminium and an outer tubular cylinder of foamed polyurethane. The printing cylinder produces a sharp imprint of high quality at high peripheral speeds, e.g., 200 meters/minute of the printing cylinder.

9 Claims, 3 Drawing Figures France 129/130 Patented Jan. 7, 1975 1w M? i M a 59m Ta 3 IMPRESSION CYLINDER BACKGROUND OF THE INVENTION The present invention relates to a printing cylinder for printing machines, particularly flexo -printing machines and indirect photogravure printing machines, comprising a printing block supporting sleeve mounted on a circular shaft.

French Pat. No. 389,01 1 discloses a substantially tubular sleeve adapted to be mounted on a drive shaft of square cross section. This sleeve can be secured and centered on the shaft by means of two or four screws located at either end of the sleeve. Utilizing such an even number of screws makes accurate centering of the sleeve on the shaft extemely difficult. Furthermore, the sleeve is mounted on the shaft with very little clearance, with the effect that during rotation, particularly at high speeds, the shaft will come into contact with the internal surface of the sleeve due to its deflection, whereby said deflection of the shaft will be transmitted on to the sleeve.

The prior art also discloses printing cylinders consisting of a steel sleeve mounted on a steel shaft. One disadvantage of these steel sleeves is their relatively heavy weight which normally requires two men for handling and carrying the steel sleeve from store to printing machine. If the cylindrical surface of the steel sleeve is inaccurate and differs from the proper dimensions by about 0.04 to 0.05 mm. in diameter, it will be necessary to send the impression cylinder to the machine shop for trueing-up. Such inaccuracy may be caused by the shaft of the printing cylinder receiving a slight jolt or impact while being handled, which is almost unavoidable in practice.

SUMMARY OF THE INVENTION The object of the invention is to provide a printing cylinder of the type as memtioned in the opening paragraph and which makes possible speedy and accurate centering of the cylindrical surface of the sleeve relatively to the shaft, and which is capable of producing a sharp imprint of high quality, even at relatively high peripheral speeds of the printing cylinder.

According to the invention, the printing cylinder is characterized by the fact that either end of the sleeve is provided in a manner known per se with an adjusting mechanism which is in engagement with the shaft, and that the sleeve is mounted with such clearance on the shaft that during rotation, the shaft cannot come into contact with the internal surface of the sleeve.

By constructing the printing cylinder in the said manner is achieved, in case the sleeve is not centered on the shaft with complete accuracy, i.e., with an inaccuracy of less than about 0.02 mm. in diameter, as a result of the shaft being untrue, that the impression cylinder need not be sent to the workshop for trueing-up, but before mounting the printing cylinder on the printing machine, the printing block fitter will be able to adjust and secure the sleeve relatively to the shaft by means of the adjusting mechanism provided at either end, with an accuracy of the order of 0.02 mm in diameter to thereby have the centre lines of the sleeve and the shaft coincide. As the sleeve is mounted with a suitable clearance on the shaft, during rotation, as a result of its deflection, the shaft will not come into contact with the internal surface of the sleeve, thereby preventing the deflection of the shaft from being transmitted to the surrounding sleeve. The centered sleeve, therefore, will not be distorted due to the deflection of the shaft. It has proved possible by means of such block-supporting sleeve to utilize peripheral speeds of up to as much as about 200 m/min., without reducing the quality of the imprint. Thus, the printing cylinder makes possible imprints of high quality, even at extremely high peripheral speeds, in relation to those heretofore employed, to thereby considerably increase production.

The printing cylinder according to the invention may be formed such that each adjusting mechanism consists of a plurality of adjusting screws disposed in a plane at right angles to the shaft of the sleeve, being adjustably screwed into threaded holes extending radially through the sleeve with displacement relatively to each other along the shaft periphery when utilizing the uneven number of three adjusting screws. There is thereby achieved an inexpensive and simple adjusting mechanism which, particularly when utilizing three adjusting screws, is capable of a speedy adjustment of the external cylinder surface of the sleeve relatively to the shaft, with the effect that the shaft is accurately centered within the sleeve.

Furthermore, the printing cylinder according to the invention may be characterized by the fact that the sleeve consists of an inner tubular metal cylinder and an outer tubular plastic cylinder. In a sleeve composed in this manner, the inner tubular metal cylinder will impart suitable strength and rigidity to the sleeve and enable the latter to be expediently formed with threaded holes for the adjusting screws. The outer tubular plastic cylinder has the effect of reducing the total weight of the sleeve, and at the same time the outer tubular cylinder serves as vibration damper because of the plastic.

Additionally, the printing cylinder according to the invention may be characterized by the fact that the inner tubular cylinder is steel. This results in a sleeve of high rigidity which makes possible a printing cylinder of relatively substantial length.

Also, the impression cylinder according to the invention may be characterized by the fact that the inner tubular cylinder is aluminium. This willreduce the total mass of the printing cylinder and accomplish at the same time the feature that the inner tubular cylinder damps to a much higher extent than a tubular steel cylinder oscillations resulting from undesirable vibration between printing block and the web of material to be printed. Besides, the inner tubular cylinder and with that the sleeve will possess the rigidity required when printing cylinders of short length are involved.

Finally, the printing cylinder according to the invention may be characterized by the fact that the outer tubular cylinder is made from foamed polyurethane or similar foamed material. This provides an outer tubular cylinder of particularly high resiliency to oscillations, whereby undesirable vibrations between block and web of material are substantially clamped by the material of the tubular cylinder. Also, the mass of the outer tubular cylinder and with that the sleeve is considerably reduced, which in turn minimizes deflection of the sleeve.

BRIEF DESCRIPTION OF THE DRAWING The invention will be explained below with reference to the drawing, in which FIG. 1 illustrates a printing cylinder mounted on a shaft, viewed from the side,

FIG. 2 is an enlarged scale of a partially vertical section through the left end of the printing cylinder of FIG. 1, and

FIG. 3 is a vertical section taken on the line IIIIII in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The printing cylinder illustrated in FIG. 1 comprises a sleeve 2 which, as shown in FIG. 2, consists of an inner tubular cylinder 3 and an outer tubular cylinder 4. The sleeve 2 is mounted with suitable clearance on a shaft 5. Either endbf the shaft 5 has a bore 6 in which is inserted a shaft pin 7 by pressure. When using, the printing cylinder, the shaft pins 7 are supported in bearings provided in the printing machine.

The outer tubular cylinder 4 carries a printing block (not shown).

Either end of the sleeve 2 is provided with an adjusting mechanism, e.g., in the form of an uneven number of fastening means such as adjusting screws 8, 9 and 10 which are in engagement with the shaft 5. Preferably the adjusting screws 8, 9 and 10 are disposed in a plane at right angles to the shaft of the sleeve 2, being adjustably screwed into threaded holes 11, 12 and 13. Said threaded holes 11, 12, 13 extend radially through the inner tubular cylinder 3 and a nylon bushing 14 inserted into both ends of the tubular cylinder 3 by pressure. Rather than the threaded holes 11, 12 and 13 extending through the nylon bushing 14, said holes may also extend through both the outer tubular cylinder 4 and the inner tubular cylinder. 3.

The nylon bushing 14 serves as an extension of that portion of each threaded hole l1, l2 and 13 extending through the inner tubular cylinder 3 so as to impart to the threaded holes l1, l2 and 13 a suitable thickness of material in which the adjusting screws 8, 9 and 10 may firmly engage.

A convenient number of adjusting screws may be used. In the event of using three adjusting screws 8, 9 and 10, these are given a l20 displacement relatively to each other along the periphery of the shaft 5, as shown in FIG. 3. By using specifically three adjusting screws, there is achieved an inexpensive and simple adjusting mechanism, making it possible by appropriately slackening and tightening the screws in the threaded holes 11, 12 and 13 to secure the sleeve 2 to the shaft 5 and enable adjustment thereof relatively to the shaft 5 in such a manner that the latter is accurately centered in relation to the outer cylinder surface of the outer tubular cylinder 4. By using specifically three adjusting screws 8, 9 and 10, it is further achieved that after tightening of the adjusting screws, the sleeve 2 is prevented from any rocking or tilting movement in relation to the shaft 5. g

The inner tubular cylinder 3 may be steel. This provides a sleeve 2 of high rigidity which is an advantage in case the printing cylinder is of relatively substantial length.

The inner tubular cylinder 3 may also be made from a different metal, e.g., aluminium. This will reduce the total mass of the printing cylinder and accomplish at the same time the feature that the inner tubular cylinder 3 clamps to a much higher extent than a tubular steel cylinder oscillations resulting from undesirable vibration between block and the web of material to be printed. Furthermore, the inner tubular cylinder 3 and with that the sleeve 2 will possess the rigidity required when printing cylinders of short length are involved.

The outer tubular cylinder 4 may be made from foamed polyurethan or similar foamed material. This provides an outer tubular cylinder 4 of particularly high resiliency to oscillations, whereby undesirable vibrations between printing block and web of material are substantially damped by the material of the tubular cylinder 4 such that there is obtained a clean-cut imprint of high quality, even when the printing cylinder is rotated at high peripheral speeds, e.g., 200 m/min.

When the printing cylinder is rotating, the shaft 5, of steel for instance, will have a certain deflection which is at its peak at the centre portion of the shaft 5 between the supporting bearings of the printing machine. This deflection will increase at higher peripheral speeds of the shaft 5. However, the deflection of the shaft 5 will not be transmitted on to the inner tubular cylinder 3 as in the first place, the adjusting mechanism in the form of adjusting screws 11, 12 and 13 is located at either end of the sleeve 2 close to the shaft pins 7 which are supported by the bearings of the printing machine and therefore have no deflection. Secondly, the deflection of the shaft 5, for instance the centre portion, will not cause the shaft 5 to come into contact with the internal surface of the inner tubular cylinder 3 as by means of the adjusting screws ll, 12 and 13 the shaft 5 is suitably spaced from the inner tubular cylinder 3. The embodiment illustrated in the drawing of the printing cylinder comprising an adjusting mechanism at either end of-the sleeve 2 and an outer tubular cylinder of foamed polyurethan has demonstrated in practice the achievement of some surprisingly good results in the form of accurate and sharp imprints without ink smudges on the web of material. In using a known printing cylinder of steel accurately centered on its steel shaft, it proved impossible in the test to rotate the printing cylinder at a peripheral speed higher than 50 m/min. in order to ensure highquality imprints. By using the same block (a rubber block), the printing cylinder according to the present invention made it possible to employ peripheral speeds of up to about 200 m/min. without reducing the quality of the imprint. Thus, the printing cylinder according to the invention makes possible high-quality imprints at high peripheral speeds, which means a considerable increase of production.

The sleeve 2, composed of the inner tubular cylinder 3 and the outer tubular cylinder 4, is relatively inexpensive to manufacture such that it will frequently be advantageous to secure a printing block permanently to the outer tubular cylinder 4, which means that the sleeve 2 will be used only when a web of material is to be impressed with the subject printing block. This eliminates adjustment of the printing block on the sleeve 2 when this block is to be used in the printing machine.

In case different printing machines have been adapted to match the same shaft 5, the latter need not be stored together with the sleeve 2 with the block attached thereto when the latter is not to be used, but by adjusting the adjusting screws 8, 9 and 10, the sleeve 2 is readily disengaged from the shaft 5, to thereby make it possible to use detached sleeves 2 for the said adapted printing machinery.

It is an important advantage of the printing cylinder according to the invention that before mounting the printing cylinder on the printing machine. the block fitter will have no difficulty in setting or adjusting the shaft 5, as required, in relation to the cylinder surface of the sleeve 2, without the necessity for sending the printing cylinder to the workshop for realignment.

The outer tubular cylinder 4 and the inner tubular cylinder 3 are expediently made in a cylindrical steel mould having a base which includes a central hole for receiving and centering one end of the inner tubular cylinder 3, and which steel mould has an upper removable end flange with a corresponding central hole for receiving and centering the upper end of the tubular cylinder 3, the latter being assumed to have a substantially vertical position. The cylindrical steel mould has an inner cylindrical surface matching the outer diameter of the outer tubular cylinder 4, and which is polished. The outer tubular cylinder 4 is formed from a fluid mixture of polyurethane and a foaming agent, said mixture being poured into the cylindrical steel mould, after which foaming takes place.

During the foaming step, the steel mould is both revolved and tilted. Due to the fact that in this method the ends of the inner tubular cylinder 3 are received in respective holes provided in the base and upper end flange of the steel mould, the outer tubular cylinder 4 will terminate short of the end surfaces of the inner tubular cylinder 3, as shown in FIG. 2.

In such a case it will be expedient to use the above described nylon bushing or annulus 14.

The printing cylinder according to the invention is suitable for printing machines, particularly flexoprinting machines and indirect photogravure printing machines.

In the case of the outer tubular cylinder of the sleeve 2 being made from foamed polyurethane the outer surface of the outer tubular cylinder 4 may according to the invention be provided with a layer of metal, e.g., copper, zinc, magnesium, or aluminium. If, for instance, the outer tubular cylinder 4 of foamed polyurethane is coated with a copper layer it will be possible to make a photogravure cylinder according to the normal process of manufacture, as the picture or the text to be printed may be engraved or etched in the copper layer. Such a sleeve is not only suitable as flexo-printing cylinder or indirect photogravure cylinder but also as photogravure cylinder. By engraving or etching directly in the metal layer as mentioned use of the known printing rubber blocks is completely avoided. Furthermore, the metal layer has a stiffening effect on the sleeve 2.

Moreover, in the case of the outer tubular cylinder 4 of the sleeve being made from foamed polyurethane the outer surface of the outer tubular cylinder 4 may be provided with a layer of light-sensitive material, especially a polymer, in which the molecular structure has been made sensitive to ultraviolet light. Hereby it is possible to make a printing cylinder for flexo-printing in a cheaper and better way than hitherto, so that use of a separate rubber printing block is avoided. Compared to rubber blocks the printing block formed by the light-sensitive material, especially polymer, is also advantageous by having a superior wearability, so that the durability of the printing block is increased.

Use of the known printing rubber blocks has the disadvantage that the manufacture hereof is both an expensive and slow process, because first a metal printing block of, e.g., zinc or magnesium has to be made, and then a matrix is to be cast on the basis of this printing block, and finally, by means of the matrix a rubber block is cast. In most cases this must be ground on its back in order to obtain a sufficiently precise thickness.

The thickness of the surface layer of metal or lightsensitive material may vary dependent on the present printing task.

The present invention is not confined to the embodiment illustrated here, but may be modified in many ways within the scope of protection according to the subsequent patent claims.

I claim:

l. A printing cylinder for printing machines, particularly flexo-printing machines and indirect photogravure printing machines, comprising a block-supporting sleeve mounted on a circular shaft wherein one end of the sleeve is provided with adjusting means which is in engagement with the shaft the sleeve is mounted with such clearance on the shaft that during rotation, the shaft cannot come into contact with the internal surface of the sleeve, said adjusting means consisting of an uneven number of adjustable fastening means, said fastening means being adapted for adjustment of the center line of the sleeve relative to the center line of the shaft.

2. The cylinder according to claim 1 wherein the fastening means are three adjusting screws disposed in a plane at right angles to the shaft of the sleeve, said screws being adjustably screwed into threaded holes extending radially through the sleeve with a displacement relatively to each other along the periphery of the shaft.

3. The cylinder according to claim 1 wherein the sleeve comprises an inner tubular cylinder made of metal metal and an outer tubular cylinder made of plastic.

4. The cylinder according to claim 3, wherein the inner tubular cylinder is made of steel.

5. The cylinder according to claim 3, wherein the inner tubular cylinder is made of aluminum.

6. The cylinder according to claim 3 wherein the outer tubular cylinder is made from foamed polyurethane or similar foamed material.

7. The cylinder according to claim 6, wherein the outer surface of the outer tubular cylinder is provided with a layer of copper, zinc, magnesium, or aluminum.

8. The cylinder according to claim 6, wherein the outer surface of the outer tubular cylinder is provided with a layer of a light-sensitive material in which the molecular structure has been made sensitive to ultraviolet light.

9. The cylinder according to claim 8 wherein the layer of said light sensitive material is made of a polymer. 

1. A printing cylinder for printing machines, particularly flexo-printing machines and indirect photogravure printing machines, comprising a block-supporting sleeve mounted on a circular shaft wherein one end of the sleeve is provided with adjusting means which is in engagement with the shaft the sleeve is mounted with such clearance on the shaft that during rotation, the shaft cannot come into contact with the internal surface of the sleeve, said adjusting means consisting of an uneven number of adjustable fastening means, said fastening means being adapted for adjustment of the center line of the sleeve relative to the center line of the shaft.
 2. The cylinder according to claim 1 wherein the fastening means are three adjusting screws disposed in a plane at right angles to the shaft of the sleeve, said screws being adjustably screwed into threaded holes extending radially through the sleeve with a 120* displacement relatively to each other along the peripHery of the shaft.
 3. The cylinder according to claim 1 wherein the sleeve comprises an inner tubular cylinder made of metal metal and an outer tubular cylinder made of plastic.
 4. The cylinder according to claim 3, wherein the inner tubular cylinder is made of steel.
 5. The cylinder according to claim 3, wherein the inner tubular cylinder is made of aluminum.
 6. The cylinder according to claim 3 wherein the outer tubular cylinder is made from foamed polyurethane or similar foamed material.
 7. The cylinder according to claim 6, wherein the outer surface of the outer tubular cylinder is provided with a layer of copper, zinc, magnesium, or aluminum.
 8. The cylinder according to claim 6, wherein the outer surface of the outer tubular cylinder is provided with a layer of a light-sensitive material in which the molecular structure has been made sensitive to ultra-violet light.
 9. The cylinder according to claim 8 wherein the layer of said light sensitive material is made of a polymer. 